Hypocalcemia

Diagnosis

Indications for Testing

• Suspect when symptoms occur and serum calcium is low

Laboratory Testing

• Initial testing – serum calcium and albumin [corrected calcium = measured total calcium +0.8 (4.0-serum albumin)], serum phosphorus, serum magnesium, serum creatinine
• If calcium low, consider repeat testing or ionized calcium
  • Ionized calcium does not need to be corrected for hypoalbuminemia, but should be corrected for pH
• If hypocalcemia is confirmed, order intact parathyroid hormone (PTH)
  • Intact PTH
    • Elevated PTH, normal or high phosphorus, normal magnesium, high creatinine – renal failure/pseudohypoparathyroidism
    • Elevated PTH,  normal or low phosphorus, normal magnesium, normal creatinine
      • Consider vitamin D testing
        • Low vitamin D 25(OH) – vitamin D deficiency
    • Low PTH, normal or high phosphorus, normal creatinine, low or normal magnesium – hypoparathyroidism or hypomagnesemia
    • Normal PTH, normal or low phosphorus, normal creatinine, normal magnesium, low albumin – hypoalbuminemia (pseudohypocalcemia)

Differential Diagnosis

• Acute hypokalemia
• Hypoparathyroidism
• Vitamin D deficiency
• Magnesium deficiency
• Clostridium tetani
• Metabolic abnormalities
• Anxiety disorder

Monitoring

Clinical Background

Hypocalcemia may be noted either acutely or chronically in hospitalized patients and outpatients.

Epidemiology

• Prevalence – occurs in 12-80% of critically ill patients

Etiology

• Acute hypocalcemia – intensive care unit patients (acute pancreatitis, sepsis)
• Hypoparathyroidism 
  • Autoimmune
    • Associated with polyglandular syndrome 1
    • Symptoms – chronic mucocutaneous candidiasis, alopecia, vitiligo
    • Autosomal recessive inheritance
  • Acquired
    • Surgical removal of parathyroids
    • Radiation-induced parathyroid destruction
    • Metastatic infiltration of glands (rare)
  • Pseudohypoparathyroidism
    • Resistance to parathyroid hormone
  • Genetic syndromes
    • DiGeorge and velocardiofacial syndrome
      • Rare congenital disorder
      • Symptoms – cardiac, facial, thymic, thyroid abnormalities
        • Severe early childhood infections
      • Learning disorders
      • Genetics – rearrangements on chromosome 22 (TBX1 gene)
    • Familial hypocalcemias – eg, including Bartter syndrome subtype V and Gitelman syndrome
    • X-linked hypoparathyroidism
    • Mitochondrial disorders with hypoparathyroidism
• Vitamin D deficiency
  • Malabsorption
  • Inadequate diet/sunlight
• Magnesium deficiency
  • Malabsorption
  • Inadequate diet
  • Alcoholism

Pathophysiology

• Serum calcium concentration kept within a narrow physiologic range
• Control of calcium by parathyroid hormone, vitamin D (1,25), calcium, and phosphate

Clinical Presentation

• Acute
  • Neuromuscular – tetany, paresthesias, muscle spasms (Chvostek and Trousseau signs)
  • Neuropsychiatric – anxiety, hallucinations, confusion
  • Cardiovascular – bradycardia, ventricular arrhythmias, cardiac collapse
• Chronic
  • Neuropsychiatric – cognitive deficits, extrapyramidal symptoms
  • Dermatologic – dermatitis, dry skin
  • Dental – enamel hypoplasia
  • Ophthalmologic – cataracts

Treatment

• Treat according to etiology
• Calcium analogues – may require intravenous calcium depending on calcium level
• Vitamin D analogues

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Parathyroid Hormone, Intact with Calcium 0070172 Method: Quantitative Electrochemiluminescent Immunoassay
Calcium, Ionized, Whole Blood 0020140 Method: Ion-Selective Electrode/pH Electrode	Available only to University of Utah patients

Diagnostic Algorithm

  Hypocalcemia Testing Algorithm